The present invention relates to a method for producing multifilaments. Multifilaments formed of polyolefins such as polypropylene and polyethylene are used to make pile yarns for ropes, nets, and carpets or as raw yarns for nonwoven fabrics.
In general, to manufacture multifilaments from thermoplastic resins, a number of molten filaments extruded through a spinneret are cooled in an ambient air stream by passage through a cooling duct less than 3-5 m long as they are taken up with drafting being effected at a comparatively high speed of approximately 300 m/min. Thereafter, the filaments are drawn, crimped, and otherwise processed in separate steps.
With the recent improvement in the performance of winders, a method called "direct spin and draw" has been proposed to perform a continuous process including the steps of spinning, drawing, and crimping. However, this method is incapable of producing high-strength multifilaments having satisfactory fiber strength.